Solenoid device with sensor

ABSTRACT

A solenoid device including pressure altering means for altering an output pressure of the solenoid device; and an actuator for providing an actuating signal to said pressure altering means; wherein the solenoid device further includes a sensor arranged to sense a control value of the solenoid device, and a controller which receives a request and is arranged to control delivery of power to the actuator with feedback from the sensor until the control value meets the request.

FIELD OF THE INVENTION

The present invention relates to a solenoid device and, moreparticularly but not exclusively, to a solenoid spool valve having anintegrated pressure sensor which provides improved performancecharacteristics when the solenoid spool valve is used in acommunications network of a vehicle or system.

BACKGROUND OF THE INVENTION

A modern vehicle typically has a large number of electronic controlunits (ECU) for various subsystems. The biggest processor is commonlythe engine control unit, however other ECUs are used for controllingother devices in the vehicle, such as the transmission, airbags,antilock braking system, cruise control, electric power steering, audiosystems, windows, doors, mirror adjustment, battery and rechargingsystems for hybrid/electric cars, etc. Some of these form independentsubsystems, but communications among others are essential. A subsystemmay need to control actuators or receive feedback from sensors. TheController-Area Network (CAN) is a standard vehicle bus orcommunications network devised to fill this need.

The applicant is aware that existing systems have sensors elsewhere on ahydraulic circuit for sensing pressure delivered by solenoid valves. Theapplicant has determined that such systems may be improved, at least inso far as performance and maintenance are concerned.

The applicant has also identified that current design high flowsolenoids have an equal area spool, meaning that lands of the spool havethe same external dimension, usually the outside diameter, resulting inthe lands having the same surface area for driving the spool in responseto fluid pressure against the lands. To increase the pressure obtainedfrom the current design solenoid spool valves requires the spooldiameter to be increased. As the diameters of each of the lands on thespool increase, the force against a diaphragm of the solenoid spoolvalve increases, necessitating a magnet (coil) size of anelectromagnetic actuator to be increased. The applicant has determinedthat it would be desirable to obviate the necessity to increase themagnet (coil) size with pressure capacity of the solenoid spool valve.

Furthermore, the applicant has also identified that increasing diametersof all lands on the spool in accordance with current practice typicallyincreases leakage to an exhaust port of the solenoid spool valve,requiring a larger pump to compensate for the leakage.

Examples of the invention seek to solve, or at least ameliorate, one ormore disadvantages of previous solenoid spool valves.

SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided a solenoiddevice including pressure altering means for altering an output pressureof the solenoid device; and an actuator for providing an actuatingsignal to said pressure altering means; wherein the solenoid devicefurther includes a sensor arranged to sense a control value of thesolenoid device, and a controller which receives a request and isarranged to control delivery of power to the actuator with feedback fromthe sensor until the control value meets the request.

Preferably, the solenoid device is a solenoid spool valve including aspool valve having a sleeve provided with a supply port, a control port,and a spool supported in the sleeve for axial displacement within thesleeve; and an electromagnetic actuator for providing an axial driveforce to said spool in a first axial direction; wherein the solenoidspool valve further includes a sensor arranged to sense a control valueof the spool valve, and a controller which receives a request and isarranged to control delivery of power to the electromagnetic actuatorwith feedback from the sensor until the control value meets the request.

More preferably, the sensor is a pressure sensor, the supply port is asupply pressure port, the control port is a control pressure port, thecontrol value is a control pressure, the request is in the form of apressure request, and the controller controls delivery of power to theelectromagnetic actuator with feedback from the pressure sensor untilthe control pressure meets the pressure request.

Preferably, the controller is in the form of a control circuit. Morepreferably, the control circuit is arranged to receive the pressurerequest from a communications network. Even more preferably, thecommunications network is a Controller-Area Network.

Preferably, the pressure sensor is arranged to sense the controlpressure of the spool valve at a location inside the sleeve.

In a preferred form, the controller is arranged to adaptively learncurrent provided to the electromagnetic actuator in relation to pressuresensed, such that the solenoid spool valve is self-compensating.

Preferably, the controller is mounted relative to the sleeve.

It is preferred that the solenoid spool valve including the pressuresensor and controller are provided as a unitary module.

Preferably, the solenoid spool valve further includes an exhaust port,the spool has a first piston with a first land for opening/closing thesupply pressure port and a second piston with a second land foropening/closing the exhaust port, wherein the first piston has a largerpiston face surface area in fluid communication with the controlpressure port than does the second piston.

Preferably, the first piston has one piston face (b) in fluidcommunication with the control pressure port arranged such that force offluid against said one piston face acts on the spool in an axialdirection away from the electromagnetic actuator, and an opposite pistonface (a) in fluid communication with a feedback orifice arranged suchthat force of fluid against said opposite piston face acts on the spoolin an axial direction toward the electromagnetic actuator.

More preferably, the feedback orifice supplies fluid at the same controlpressure as the control pressure port. Even more preferably, thefeedback orifice is in fluid communication with the control pressureport. In one example, the orifice is formed as a duct extending throughthe first piston to communicate with the control pressure port.

Preferably, the face (c) of the second piston in fluid communicationwith the control pressure port is arranged such that force of fluidagainst said face acts on the spool in an axial direction toward theelectromagnetic actuator.

Preferably, the spool is arranged such that, the combined force on thespool from fluid against piston faces of the spool is independent of thetransverse extent of the first piston, owing to equal and opposite facesurface areas of the first piston. More preferably, the first piston iscylindrical and the combined force on the spool from fluid againstpiston faces of the spool is independent of an outside diameter of thefirst piston.

Preferably, the spool is arranged such that, the combined force on thespool from fluid against piston faces of the spool is given by theequation:

combined force=A+C−B,

where A, B and C are the fluid forces acting on faces a, b and c,respectively.

In a preferred form, the first piston has a larger diameter than thesecond piston. More preferably, as a result of the larger diameter ofthe first piston, the valve has relatively high flow from the supplypressure port to the control pressure port and relatively low flow fromthe control pressure port to the exhaust port.

In accordance with another aspect of the present invention, there isprovided a range of solenoid spool valves, each of which is as describedabove, wherein each of the solenoid spool valves has a different firstpiston diameter to second piston diameter ratio to provide differentpressure capabilities, and wherein each of the solenoid spool valves hasan identical electromagnetic actuator.

In one particular example, each of the solenoid spool valves has adifferent first piston diameter, and the same second piston diameter.

However, a learned person can appreciate that the technology describedherein does not need to be limited to solenoids having spool valves andcould be incorporated into other solenoid types that can alter pressurethrough other control means, for example, by controlling the exhaustingof oil from a control chamber, fed by a controlled source, ie anorifice, in a controlled manner, thus effecting pressure control. Theintegration of the pressure sensor and controls in this case would bekey to the repeatable pressure output from this previouslynon-self-regulating system/solenoid.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described, by way of non-limiting example only, withreference to the accompanying drawings in which:

FIG. 1 is a solenoid spool valve with pressure sensor in accordance withan example of the present invention;

FIG. 2( a) is a diagrammatic cross-sectional view of a solenoid spoolvalve in accordance with a first example;

FIG. 2( b) is a diagrammatic cross-sectional view of a solenoid spoolvalve in accordance with a second example;

FIG. 2( c) is a diagrammatic cross-sectional view of a solenoid spoolvalve in accordance with a third example;

FIG. 2( d) is a diagrammatic cross-sectional view of a solenoid spoolvalve in accordance with a fourth example;

FIG. 3 shows detail of a spool of a solenoid spool valve the same orsimilar to those shown in FIGS. 2( a) to 2(d);

FIG. 4 is a diagrammatic view of an example system incorporating asolenoid spool valve in accordance with the invention;

FIG. 5 is a diagrammatic view of another example system incorporating aplurality of solenoid spool valves in accordance with the invention; and

FIG. 6 is a diagram showing an on board controller with a series ofpossible CAN nodes.

DETAILED DESCRIPTION

With reference to FIG. 1 of the drawings, there is provided a solenoidspool valve 10 used for supplying varying pressures from a system supplypressure to an object (such as, for example, a friction clutch). Thesolenoid spool valve 10 is advantageously provided with a pressuresensor 46 and a controller 48 to achieve improvedperformance/convenience when used in a communications network such as aController-Area Network (CAN).

More specifically, the applicant has determined that existing systemstypically use a sensor elsewhere on a hydraulic circuit, separate to thesolenoid spool valve. The applicant has determined that sucharrangements are disadvantageous, particularly when it comes torebuilding and maintenance. Specifically, as existing systems supply thesolenoid spool valve with a current and use an external pressure sensorto sense pressure achieved by the solenoid spool valve, components ofthe system separate to the solenoid spool valve may have to adapt towear of the solenoid spool valve as it may deteriorate over time andchange its characteristics. Then, when the solenoid spool valve isreplaced with a fresh solenoid spool valve, the remainder of the systemmust re-learn to accommodate the new solenoid spool valve which hasdifferent characteristics to the replaced solenoid spool valve. Theapplicant has determined that it would be advantageous for there to beprovided a solenoid spool valve which has its own pressure sensor andcontroller such that the solenoid spool valve is sent a pressure requestrather than a current, as is typical in existing systems. In this way,the components of the system external to the solenoid spool valve do notneed to compensate for the change in characteristics of the Solenoidspool valve which are dealt with internally of the solenoid spool valveby virtue of its ability to be self-compensating. The pressure sensor 46is in the control pressure circuit of the solenoid spool valve 10, andthere is feed from the CAN such that an input pressure may be requestedand controlled at the source of the signal (ie. within the solenoid).The pressure signal is fed back to the solenoid controller 48 from thepressure sensor 46.

More specifically, the solenoid spool valve 10 includes a spool valve 12having a sleeve 14 provided with a supply pressure port 16, a controlpressure port 18 and a spool 22 supported in the sleeve 14 for axialdisplacement within the sleeve 14. The solenoid spool valve 10 alsoincludes an electromagnetic actuator 24 for providing an axial driveforce to the spool 22 in a first axial direction away from theelectromagnetic actuator 24 so as to operate the spool valve 12. Thesolenoid spool valve 10 further includes the pressure sensor 46 arrangedto sense a control pressure of the spool valve 12, and the controller 48which receives a pressure request and is arranged to control delivery ofpower to the electromagnetic actuator 24 with feedback from the pressuresensor 46 to meet the pressure request.

The controller 48 may receive the pressure request from thecommunications network by way of communication means such as, forexample, communication wires 50. Similarly, the pressure sensor 46 maybe coupled in communication with the controller 48 by way ofcommunication wires 52. The controller 48 shown in FIG. 1 supplies powerto the electromagnetic actuator 24 by way of power lines 54. However, analternative to this arrangement can be the combining of the power andCAN wires in that the CAN signal is “injected” on top of the power wiresthus requiring only 2 wires to be connected to the solenoid assembly.

In the example shown, the pressure sensor 46 is located in a cavity ofthe sleeve 14 near a bore of the spool valve 12 so as to sense thepressure of fluid (gas or liquid) in the control pressure circuit incommunication with the control pressure port 18. The controller 48 ismounted relative to the sleeve 14 and may be arranged to adaptivelylearn current provided to the electromagnetic actuator 24 in relation topressure sensed by the pressure sensor 46, such that the solenoid spoolvalve 10 is self-compensating.

Advantageously, as the solenoid spool valve 10 including the pressuresensor 46 and controller 48 is provided as a unitary module, the entiremodule is able to be replaced at the end of its life without any needfor an external controller to adapt to the new unit as it performs itsown conversion of the desired pressure to the power requirements of theelectromagnetic actuator 24.

In the example shown in FIG. 1, the solenoid spool valve 12 is a twoland high flow solenoid spool valve which enables higher controlpressures to be used without necessitating a correspondingly largerelectromagnetic actuator. A similar solenoid spool valve 12 is shown inFIG. 2( a), and is described below. In the subsequent figures, there areshown examples of alternative solenoid spool valves 12 which may also beadapted to include a pressure sensor 46 and controller 48 in the mannershown in FIG. 1 so as to embody alternative configurations of thepresent invention.

With reference to FIG. 2( a) there is shown a solenoid spool valve 10used for supplying varying pressures from a system supply pressure to anobject (such as, for example, a friction clutch). The solenoid spoolvalve 10 shown has an increased supply pressure diameter of the spoolwhile leaving the regulated pressure end of the spool at the originaldiameter. By virtue of this configuration, the resultant force on adiaphragm of the valve 10 is independent of the increased supplypressure diameter.

More specifically, the solenoid spool valve 10 includes a spool valve 12having a sleeve 14 provided with a supply pressure port 16, a controlpressure port 18, an exhaust port 20 and a spool 22 supported in thesleeve 14 for axial displacement within the sleeve 14. The solenoidspool valve 10 also includes an electromagnetic actuator 24 forproviding an axial drive force to the spool 22 in a first axialdirection away from the electromagnetic actuator so as to operate thespool valve 12. The spool 22 has a first piston 26 with a first land 28for opening/closing the supply pressure port 16, and a second piston 30with a second land 32 for opening/closing the exhaust port 20. The firstpiston 26 has a larger piston face surface area 34 in fluidcommunication with the control pressure port 18 than does the secondpiston 30.

The first piston 26 has one piston face (b) in fluid communication withthe control pressure port 18, arranged such that force of fluid againstthe face (b) acts on the spool 22 in an axial direction away from theelectromagnetic actuator 24. The first piston 26 also has an oppositepiston face (a) in fluid communication with a feedback orifice 36arranged such that force of fluid against the opposite piston face (a)acts on the spool 22 in an axial direction toward the electromagneticactuator 24. The feedback orifice 36 supplies fluid at the same controlpressure as the control pressure port 18. In the example shown in FIG.2( a), the feedback orifice 36 is formed in the sleeve 14 so as toprovide fluid at the control pressure to piston face (a) of the firstpiston 26.

FIGS. 2( b) to 2(d) show alternative configurations of solenoid spoolvalves 10 in accordance with other examples of the present invention.More specifically, with reference to FIG. 2( b), the solenoid spoolvalve 10 shown in this example is similar to the example shown in FIG.2( a), except in that the feedback orifice 36 is located in an end ofthe spool valve 12, rather than in a side wall of the sleeve 14. Withreference to the example shown in FIG. 2( c), the feedback orifice 36 isprovided in a sidewall of the sleeve 14 (in a manner similar to that inFIG. 2( a)), however this example differs in that the sleeve 14 isnon-circular, in contrast to the examples in FIGS. 2( a), 2(b) and 2(d).This is made evident by the cross-sectional depiction of the sleeve 14in FIG. 2( c), wherein the sleeve 14 extends to a greater degree belowthe spool 22 than it does above the spool 22.

The solenoid spool valve 10 shown in FIG. 2( d) has a feedback orifice36 formed as a duct 38 extending through the first piston 26 tocommunicate with the control pressure port 18. Also, the example shownin FIG. 2( d) incorporates a damper 40 as part of the solenoid spoolvalve 10. As can be seen, the size of the magnet 42 is common to allfour versions of the solenoid spool valve 10 shown in. FIGS. 2( a) to2(d), as all four versions use an identical electromagnetic actuator 24.

In each of the solenoid spool valves 10 shown in FIGS. 2( a) to 2(d),the face (c) of the second piston 30 in fluid communication with thecontrol pressure port 18 is arranged such that force of fluid againstthat face (c) acts on the spool 22 in an axial direction toward theelectromagnetic actuator 24.

With reference to FIG. 3, the spool 22 is arranged such that, for anystationary position of the spool valve (including when the supplypressure port 16 of the solenoid spool valve 10 is closed as shown), thecombined force on the spool 22 from fluid against piston faces of thespool 22 is independent of the transverse extent of the first piston 26.This independence is due to equal and opposite face surface areas of thefirst piston 26, which effectively cancel each other. Where the firstpiston 26 is cylindrical, the combined force on the spool 22 from fluidagainst piston faces of the spool 22 is independent of an outsidediameter of the first piston 26. With regard to the lettering shown inFIG. 3, the combined force on the spool 22 from fluid against pistonfaces of the spool 22 is given by the equation:

Combined force=A+C−B, where A, B and C are the fluid forces acting onfaces (a), (b) and (c), respectively.

In this way, the force on the annular part of surface (a) represented bythe six outermost arrows of A cancel out the forces on surface (b)represented by the six arrows of force B, such that the combined forceis truly independent of the outside diameter of the first piston 26.

Where the spool is cylindrical, the first piston 26 has a largerdiameter than the second piston 30 so that the first piston 26 has alarger piston face surface area in fluid communication with the controlpressure port 18 than does the second piston 30. As a result of thelarger diameter of the first piston 26, the valve 10 has relatively highflow from the supply pressure port 16 to the control pressure port 18and relatively low flow from the control pressure port 18 to the exhaustport 20. This is desirable, as the relatively low flow from the controlpressure port 18 to the exhaust port 20 minimises leakage such that asmaller pump may be used.

Advantageously, the ability to increase the diameter of the first piston26 enables higher control pressure to be used, assisting in theregulation of higher pressures and facilitating quick action of thesolenoid spool valve 10. Also, as the size of magnet 42 is independentof the flow area design, the pressure can be adjusted by varying thediameter of the first piston 26 while maintaining a common coil/coresize between pressure/flow variants. This may assist in maintaining anoverall short length when compared with other high flow solenoids, andfacilitates the provision of a family of solenoid designs using a commonmagnet coil/core and body.

The tunable feedback orifice 36 may have a maximised effect by beinglocated to cooperate with the largest area of the spool 22.

The solenoid spool valve 10 may have a filled canister whereby oil isprovided inside the electromagnetic actuator to change the naturalfrequency of the solenoid spool valve 10. Also, a trimming screw 44 maybe mounted as shown in FIGS. 2( a) to 2(d).

With reference to FIG. 4, there is shown a diagrammatic view of anexample system incorporating a solenoid spool valve 10 in accordancewith the invention. In the example shown, the solenoid spool valve 10 isused in combination with a seat base/cushion 56 to control operation ofthe seat base/cushion. In particular, the solenoid spool valve 10receives information from a sensor 46 via an on board controller (OBC)48. The OBC is connected by wiring to a master controller 58.

FIG. 5 shows an example system incorporating a plurality of solenoidspool valves 10, each of which is provided with a separate OBC 48, andan individual identifier such that the individual solenoid spool valves10 are able to be operated individually. The solenoid spool valves 10are connected by communication wires 50. The communication wires 50 canbe a combination of the power and CAN wires such that the CAN signal is“injected” on top of the power wires thus requiring only two wires to beconnected to each solenoid assembly. As the communication wires 50connect to the master controller 58 in an endless loop, this allows forcontinued power and CAN communication from either direction in the eventhat a wire or connection is faulty, thus making the system more robustand failsafe.

FIG. 6 shows an OBC 48 of a solenoid spool valve 10 with a series ofpossible CAN nodes that could be used by the OBC 48 to measureresponses. More specifically, the diagram shows a range of differentsensors 46 that could be used by the OBC 48 to measure responses,depending on the nature of the request quantity type which is receivedby the OBC 48. In each case, the sensor 46 is arranged to sense acontrol value of the spool valve, and the OBC 48 receives a request andis arranged to control delivery of power to the electromagnetic actuatorof the solenoid spool valve 10 with feedback from the sensor 46 untilthe control value meets the request.

While various embodiments of the present invention have been describedabove, it should be understood that they have been presented by way ofexample only, and not by way of limitation. It will be apparent to aperson skilled in the relevant art that various changes in form anddetail can be made therein without departing from the spirit and scopeof the invention. Thus, the present invention should not be limited byany of the above described exemplary embodiments.

The CAN solenoid spool valve (CS) of examples of the present inventionis the combination of several technologies into one device that enablesthat device to:

-   -   self control its own pressure output based on a CAN signal from        a master controller;    -   be self compensating for wear;    -   be self compensating for changes in ambient conditions (ie        temperature, pressure, fluid viscosity, leakage); and    -   be able to be commonised and calibrated according to customer        requirements by simple programming.

In one variation of the design the CS includes a solenoid spool valvehaving the ability to produce varied pressure outputs, with theintegration of a pressure sensor into the control port and a smallon-board controller that is supplied power and a CAN signal from amaster controller and is able to drive the solenoid spool to achieve thedesired pressure output independent of wear, leakage, temperature andinlet pressure to achieve the desired result.

In another variation of the design the CS includes a solenoid spoolvalve having the ability to produce varied flow outputs, with theintegration of a flow sensor into the control port and a small on-boardcontroller that is supplied power and a CAN signal from a mastercontroller and is able to drive the solenoid spool to achieve thedesired flow output or speed independent of wear, leakage, temperatureand inlet pressure to achieve the desired result.

In another variation of the design the CS includes a solenoid spoolvalve having the ability to produce varied flow outputs, with theintegration of a temperature sensor into the control port and a smallon-board controller that is supplied power and a CAN signal from amaster controller and is able to drive the solenoid spool to achieve thedesired temperature independent of wear, leakage, temperature and inletpressure to achieve the desired result (ie coolant control valve).

In yet another variation of the design the CS includes a solenoid spoolvalve having the ability to produce varied flow outputs, with theintegration of a speed sensor to measure engine speed and a smallon-board controller that is supplied power and a CAN signal from amaster controller and is able to drive the solenoid spool to achieve thedesired speed output independent of wear, leakage, temperature and inletpressure to achieve the desired result.

In still another variation of the design the CS includes an actuatormotor having the ability to produce position control, the integration ofa position sensor onto the output and a small on-board controller thatis supplied power and a CAN signal from a master controller and is ableto drive the actuator to achieve the desired position independent ofwear, leakage, temperature and voltage supply.

The CS controller is connected to power and can be interconnected to themaster controller via CAN as separate wires, or can also be linked viaCAN-Over-Power, radio links, Bluetooth or otherwise as examples. The CScan also use other sensors already existing on the CAN to effect thedesired results and monitor its performance.

The CS would automatically adjust itself to wear over its lifetime andadjust itself to suit its environment.

The CS can be “labelled” to have a distinguishing number or identifierso that many solenoids of the same type can be used on the same CAN linewhere only the identifier is different so that each solenoid has its ownunique ID address so that when CAN requests a pressure change, it couldask each solenoid individually to perform the change as requested andwhen requested.

Using an example of a CS controlling pressure, the following is offered:

-   (i). Ignition is turned on in vehicle and engine is started-   (ii). Driver engages Drive gear-   (iii). Master controller sends a signal to the solenoid via CAN    requesting a ramp up of pressure over time to effect a smooth    engagement of drive gear in the transmission-   (iv). The solenoid self regulates the pressure at the desired    increasing rate as instructed, compensating for wear, leakage and    temperature to achieve the desired rate of change of pressure-   (v). Once the function is completed, the solenoid sends a signal    back over CAN to the master controller to confirm the function    requested has completed, or, the solenoid is unable to complete the    task and the reason eg. pressure too low, pressure too high, etc    (error message whereby the Master controller adopts a failsafe mode)

Variations of the invention include but are not limited to:

-   (a). An Idle Air Control Solenoid for Internal Combustion Engines    with an integrated speed sensor and controller that will adjust air    bleed bypass to the engine at idle to control idle speed at the    request of the engine ECU over CAN. The idle air solenoid would    automatically adjust the airflow to achieve the desired engine idle    speed based on its own integrated speed sensor.-   (b). A centre-neutral logic control solenoid that would control    hydraulic oil in industrial/mining machines where the integrated    sensor(s) and controller would perform the dual purpose of providing    control pressure to the correct pressure port as directed via CAN    (left on or right on) and would feed back information to the main    machine control unit if the incorrect pressure has been achieved, or    if there is pressure caused by leakage into the control circuit that    has not been requested by the solenoid controller, thus enabling a    safety shutdown of the machine due to unplanned/uncommanded actions.-   (c). Any device that requires flow control, speed control or    position control that is normally controlled via the supplying of    current or voltage to the device to achieve control whereby the    resulting feedback is not monitored and corrected for at the device    itself by the use of integrated sensors and local control.

The reference in this specification to any prior publication (orinformation derived from it), or to any matter which is known, is not,and should not be taken as an acknowledgment or admission or any form ofsuggestion that that prior publication (or information derived from it)or known matter forms part of the common general knowledge in the fieldof endeavour to which this specification relates.

Throughout this specification and the claims which follow, unless thecontext requires otherwise, the word “comprise”, and variations such as“comprises” and “comprising”, will be understood to imply the inclusionof a stated integer or step or group of integers or steps but not theexclusion of any other integer or step or group of integers or steps.

1.-28. (canceled)
 29. A solenoid device in the form of a module, themodule including pressure altering means for altering an output pressureof the solenoid device; and an actuator for providing an actuatingsignal to said pressure altering means; wherein the solenoid devicefurther includes a sensor arranged to sense a control value of thesolenoid device, and a controller which receives a request and isarranged to control delivery of power to the actuator with feedback fromthe sensor until the control value meets the request.
 30. The solenoiddevice as claimed in claim 29, wherein the solenoid device is a solenoidspool valve including a spool valve having a sleeve provided with asupply port, a control port, and a spool supported in the sleeve foraxial displacement within the sleeve; and an electromagnetic actuatorfor providing an axial drive force to said spool in a first axialdirection; wherein the solenoid spool valve further includes a sensorarranged to sense a control value of the spool valve, and a controllerwhich receives a request and is arranged to control delivery of power tothe electromagnetic actuator with feedback from the sensor until thecontrol value meets the request.
 31. The solenoid spool valve as claimedin claim 30, wherein the sensor is a pressure sensor, the supply port isa supply pressure port, the control port is a control pressure port, thecontrol value is a control pressure, the request is in the form of apressure request, and the controller controls delivery of power to theelectromagnetic actuator with feedback from the pressure sensor untilthe control pressure meets the pressure request.
 32. The solenoid spoolvalve as claimed in claim 31, wherein the controller is in the form of acontrol circuit.
 33. The solenoid spool valve as claimed in claim 32,wherein the control circuit is arranged to receive the pressure requestfrom a communications network.
 34. The solenoid spool valve as claimedin claim 33, wherein the communications network is a Controller-AreaNetwork.
 35. The solenoid spool valve as claimed in claim 31, whereinthe pressure sensor is arranged to sense the control pressure of thespool valve at a location inside the sleeve.
 36. The solenoid spoolvalve as claimed in claim 31, wherein the controller is arranged toadaptively learn current provided to the electromagnetic actuator inrelation to pressure sensed, such that the solenoid spool valve isself-compensating.
 37. The solenoid spool valve as claimed in claim 31,wherein the controller is mounted relative to the sleeve.
 38. Thesolenoid spool valve as claimed in claim 31, wherein the solenoid spoolvalve including the pressure sensor and controller are provided as aunitary module.
 39. The solenoid spool valve as claimed in claim 31,wherein the solenoid spool valve further includes an exhaust port, thespool has a first piston with a first land for opening/closing thesupply pressure port and a second piston with a second land foropening/closing the exhaust port, wherein the first piston has a largerpiston face surface area in fluid communication with the controlpressure port than does the second piston.
 40. The solenoid spool valveas claimed in claim 39, wherein the face (c) of the second piston influid communication with the control pressure port is arranged such thatforce of fluid against said face acts on the spool in an axial directiontoward the electromagnetic actuator.
 41. The solenoid spool valve asclaimed in claim 39, wherein the spool is arranged such that, thecombined force on the spool from fluid against piston faces of the spoolis independent of the transverse extent of the first piston, owing toequal and opposite face surface areas of the first piston.
 42. Thesolenoid spool valve as claimed in claim 39, wherein the first pistonhas one piston face (b) in fluid communication with the control pressureport arranged such that force of fluid against said one piston face actson the spool in an axial direction away from the electromagneticactuator, and an opposite piston face (a) in fluid communication with afeedback orifice arranged such that force of fluid against said oppositepiston face acts on the spool in an axial direction toward theelectromagnetic actuator, wherein the feedback orifice supplies fluid atthe same control pressure as the control pressure port, wherein thefeedback orifice is in fluid communication with the control pressureport, and wherein the first piston is cylindrical and the combined forceon the spool from fluid against piston faces of the spool is independentof an outside diameter of the first piston.
 43. The solenoid spool valveas claimed in claim 41, wherein the spool is arranged such that, thecombined force on the spool from fluid against piston faces of the spoolis given by the equation:combined force=A+C−B, where A, B and C are the fluid forces acting onfaces a, b and c, respectively.
 44. The range of solenoid spool valves,each of which is as claimed in claim 39, wherein each of the solenoidspool valves has a different first piston diameter to second pistondiameter ratio to provide different pressure capabilities, and whereineach of the solenoid spool valves has an identical electromagneticactuator.
 45. The solenoid device as claimed in claim 29, wherein thesensor includes one or more of the following sensor types: a flowsensor, with the control value in the form of a control flow value andthe request in the form of a flow request; a temperature sensor, withthe control value in the form of a control temperature value and therequest in the form of a temperature request; a speed sensor, with thecontrol value in the form of a control speed value and the request inthe form of a speed request; and a position sensor, with the controlvalue in the form of a control position value and the request in theform of a position request.
 46. The solenoid device as claimed in claim29, wherein the controller is arranged to receive the pressure requestfrom one or more of the following communication types: CAN,CAN-Over-Power, radio links, or Bluetooth.
 47. The solenoid spool valveas claimed in claim 34, wherein the solenoid spool valve is arranged touse other sensors already existing on the communications network. 48.The solenoid spool valve as claimed in claim 34, wherein there areseveral like solenoid spool valves in the communications network, andeach solenoid spool valve has a unique identifier to enable saidsolenoid spool valve to be operated individually.